Hainsey played professional hockey for nearly 16 years (907 games) before playing on a team that made the post-season; longer than any other player in league history and then won his first Stanley Cup in his first playoff appearance finishing second in ice time for the playoffs.[1]

After spending three seasons in the Canadiens organization, Hainsey was claimed off of waivers on November 29, 2005, by the Columbus Blue Jackets,[2] where he established himself into a leading two-way defenseman.

Hainsey won the Stanley Cup with the Penguins in 2017.

On July 2, 2008, the Atlanta Thrashers signed Hainsey to a five-year, $22.5 million contract.[3] He scored six goals to go along with 33 assists in his first season in Atlanta. He would go on to record 45 points in the next two seasons with the Thrashers. Upon their move to Winnipeg to start the 2011–12 NHL season, Hainsey recorded 10 assists in 56 games for the Jets in 2011–12.

Hainsey also played a role in the negotiations of the 2012–13 NHL lockout. After a day of marathon bargaining sessions on December 5, 2012, Hainsey emerged to tell the media that both sides planned to meet again the next day.[4]

On September 12, 2013, Hainsey signed a one-year, $2 million contract with the Carolina Hurricanes after the team announced defenseman Joni Pitkanen would miss the season due to injury. On June 24, 2014, Hainsey signed a three-year, $8.5 million contract extension with the Hurricanes.[5]

On February 23, 2017, Hainsey, in the final year of his contract, was traded to the Pittsburgh Penguins in exchange for a 2017 second-round draft pick and Danny Kristo, a minor league forward.[6] Interestingly, it was the first time he had been traded in his lengthy career.[7] It was with the Penguins that, after 907 career NHL games and beating Olli Jokinen's previous playoff games drought record, Hainsey finally made his Stanley Cup playoffs debut against his former team, the Columbus Blue Jackets, on April 12, 2017.[1] On June 11, 2017, he won the Stanley Cup with the Pittsburgh Penguins.[8]

Hainsey left the Penguins after his short but successful tenure as a free agent, signing to a two-year, $6 million contract with the Toronto Maple Leafs on July 1, 2017.[9] Hainsey was signed to replace departing defenceman Matt Hunwick, who coincidentally signed with the Penguins that same day.[9] Hainsey made his season debut playing alongside Morgan Rielly.